Konishi, Morikazu (Kanagawa, JP)

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10/547383

02/12/2008

02/19/2004

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Sony Corporation (JP)

313/306

313/309, 315/169.300

G09G3/22

315/169.3, 313/307, 313/309, 313/306, 313/308

6278228	Cold cathode field emission device and cold cathode field emission display	August, 2001	Iwase et al.	313/306
7064493	Cold cathode electric field electron emission display device	June, 2006	Konishi	315/169.1

JP09090898	April, 1997			COLD CATHODE DRIVING CIRCUIT AND ELECTRON BEAM DEVICE USING THE SAME
JP2000323013	November, 2000			COLD CATHODE FIELD ELECTRON EMISSION ELEMENT AND ITS MANUFACTURE AS WELL AS COLD CATHODE FIELD ELECTRON EMISSION TYPE DISPLAY DEVICE
JP2001243893	September, 2001
JP2003031150	January, 2003
JP2004047408	February, 2004

International Search Report mailed May 25, 2004.
International Search Opinion mailed May 25, 2005.

Vu, David H.

Rader Fishman & Grauer PLLC
Kananen, Ronald P.

The invention claimed is:

1. A cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions, the anode panel comprising a substrate, a phosphor layer formed on the substrate, an anode electrode formed on the phosphor layer and a resistance layer for controlling a discharge current, the resistance layer being formed on the anode electrode and having a thickness of t_R (unit: μm), and the cold cathode field emission display satisfying the following expression (1),
Q>(½)C·V_A² (1) where $Q\approx \pi ·t_R·r_R^2·d_R\times \left[C_{\mathrm{m\_S}}\left(T_L-T_r\right)+Q_{\mathrm{S\_L}}+C_{\mathrm{m\_L}}\left(T_G-T_L\right)+Q_{\mathrm{L\_G}}\right]\times {10}^{-6}$ and, C: an electrostatic capacity (F) between the cold cathode field emission device and the anode electrode, V_A: a voltage (V) to be applied to the anode electrode, r_R: a radius (mm) of a vaporization-allowable region of the resistance layer, d_R: a density (g·cm⁻³) of a material constituting the resistance layer, C_m—S: a specific heat (J·g⁻¹·K⁻¹) of a material constituting the resistance layer in a solid state, T_L: a melting point (° C.) of a material constituting the resistance layer, T_r: room temperature (° C.), Q_S—L: a heat of solution (J·g⁻¹) of a material constituting the resistance layer, C_m—L: a specific heat (J·g⁻¹·K⁻¹) of a material constituting the resistance layer in a liquid state, T_G: a boiling point (° C.) of a material constituting the resistance layer, and, Q_L—G: a heat of vaporization (J·g⁻¹) of a material constituting the resistance layer.

2. The cold cathode field emission display according to claim 1, in which the cold cathode field emission device comprises: (a) a cathode electrode being formed on the supporting member and extending in a first direction, (b) an insulating layer formed on the supporting member and the cathode electrode, (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (d) an insulating film formed on the gate electrode and the insulating layer, (e) a focus electrode formed on the insulating film, (f) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and (g) an electron-emitting portion exposed in a bottom portion of the opening portion.

3. The cold cathode field emission display according to claim 2, in which the cold cathode field emission device further comprises: (h) a second resistance layer for controlling a discharge current, the second resistance layer being formed on the focus electrode and having a thickness of t′_R (unit: μm).

4. The cold cathode field emission display according to claim 1, in which the cold cathode field emission device comprises: (a) a cathode electrode being formed on a supporting member and extending in a first direction, (b) an insulating layer formed on the supporting member and the cathode electrode, (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (d) an opening portion formed through the gate electrode and the insulating layer, and (e) an electron-emitting portion exposed in a bottom portion of the opening portion.

5. The cold cathode field emission display according to claim 1, in which the anode electrode is constituted of a set of N anode electrode units (N≧2), and said “C” represents an electrostatic capacity (unit: F) between the cold cathode field emission device and the anode electrode unit.

6. A cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions, the anode panel comprising a substrate, a phosphor layer formed on the substrate, an anode electrode formed on the phosphor layer and a resistance layer for controlling a discharge current, the resistance layer being formed on the anode electrode and having a thickness of t_R (unit: μm), and the cold cathode field emission display satisfying the following expression (1),
Q>(½)C·V_A² (1) where
Q≈π·t_R·r_R²·d_R×[C_m—S(T_G−T_r)+Q_L—G]×10⁻⁶ and, C: an electrostatic capacity (F) between the cold cathode field emission device and the anode electrode, V_A: a voltage (V) to be applied to the anode electrode, r_R: a radius (mm) of a vaporization-allowable region of the resistance layer, d_R: a density (g·cm⁻³) of a material constituting the resistance layer, C_m—S: a specific heat (J·g⁻¹·K⁻¹) of a material constituting the resistance layer in a solid state, T_r: room temperature (° C.), T_G: a boiling point (° C.) of a material constituting the resistance layer, and Q_L—G: a sum (J·g⁻¹) of a heat of vaporization and a heat of solution of a material constituting the resistance layer.

7. The cold cathode field emission display according to claim 6, in which the cold cathode field emission device comprises: (a) a cathode electrode being formed on the supporting member and extending in a first direction, (b) an insulating layer formed on the supporting member and the cathode electrode, (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (d) an insulating film formed on the gate electrode and the insulating layer, (e) a focus electrode formed on the insulating film, (f) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and (g) an electron-emitting portion exposed in a bottom portion of the opening portion.

8. The cold cathode field emission display according to claim 7, in which the cold cathode field emission device further comprises: (h) a second resistance layer for controlling a discharge current, the second resistance layer being formed on the focus electrode and having a thickness of t′_R (unit: μm).

9. The cold cathode field emission display according to claim 6, in which the cold cathode field emission device comprises: (a) a cathode electrode being formed on a supporting member and extending in a first direction, (b) an insulating layer formed on the supporting member and the cathode electrode, (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (d) an opening portion formed through the gate electrode and the insulating layer, and (e) an electron-emitting portion exposed in a bottom portion of the opening portion.

10. The cold cathode field emission display according to claim 6, in which the anode electrode is constituted of a set of N anode electrode units (N≧2), and said “C” represents an electrostatic capacity (unit: F) between the cold cathode field emission device and the anode electrode unit.

11. A cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions, the anode panel comprising a substrate, a phosphor layer formed on the substrate, an anode electrode formed on the phosphor layer and a resistance layer for controlling a discharge current, the resistance layer being formed on the anode electrode and having a thickness of t_R (unit: μm), and the cold cathode field emission display satisfying the following expression (2),
t_R×10⁻²>(½)C·V_A² (2) where C: an electrostatic capacity (F) between the cold cathode field emission device and the anode electrode, and V_A: a voltage (V) to be applied to the anode electrode.

12. The cold cathode field emission display according to claim 11, in which the cold cathode field emission device comprises: (a) a cathode electrode being formed on the supporting member and extending in a first direction, (b) an insulating layer formed on the supporting member and the cathode electrode, (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (d) an insulating film formed on the gate electrode and the insulating layer, (e) a focus electrode formed on the insulating film, (f) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and (g) an electron-emitting portion exposed in a bottom portion of the opening portion.

13. The cold cathode field emission display according to claim 12, in which the cold cathode field emission device further comprises: (h) a second resistance layer for controlling a discharge current, the second resistance layer being formed on the focus electrode and having a thickness of t′_R (unit: μm).

14. The cold cathode field emission display according to claim 11, in which the cold cathode field emission device comprises: (a) a cathode electrode being formed on a supporting member and extending in a first direction, (b) an insulating layer formed on the supporting member and the cathode electrode, (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (d) an opening portion formed through the gate electrode and the insulating layer, and (e) an electron-emitting portion exposed in a bottom portion of the opening portion.

15. The cold cathode field emission display according to claim 11, in which the anode electrode is constituted of a set of N anode electrode units (N≧2), and said “C” represents an electrostatic capacity (unit: F) between the cold cathode field emission device and the anode electrode unit.

16. A cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions, the anode panel comprising a substrate, a phosphor layer formed on the substrate and an anode electrode formed on the phosphor layer, each cold cathode field emission device comprising: (A) a cathode electrode being formed on a supporting member and extending in a first direction, (B) an insulating layer formed on the supporting member and the cathode electrode, (C) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (D) an insulating film formed on the gate electrode and the insulating layer, (E) a focus electrode formed on the insulating film, (F) a resistance layer for controlling a discharge current, the resistance layer being formed on the focus electrode and having a thickness of t_R (unit: μm), (G) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and (H) an electron-emitting portion exposed in a bottom portion of the opening portion, and the cold cathode field emission display satisfying the following expression (3),
Q>(½)C·V_A² (3) where $Q\approx \pi ·t_R·r_R^2·d_R\times \left[C_{\mathrm{m\_S}}\left(T_L-T_r\right)+Q_{\mathrm{S\_L}}+C_{\mathrm{m\_L}}\left(T_G-T_L\right)+Q_{\mathrm{L\_G}}\right]\times {10}^{-6}$ and, C: an electrostatic capacity (F) between the focus electrode and the anode electrode, V_A: a voltage (V) to be applied to the anode electrode, r_R: a radius (mm) of a vaporization-allowable region of the resistance layer, d_R: a density (g·cm⁻³) of a material constituting the resistance layer, C_m—S: a specific heat (J·g⁻¹·K⁻¹) of a material constituting the resistance layer in a solid state, T_L: a melting point (° C.) of a material constituting the resistance layer, T_r: room temperature (° C.), Q_S—L: a heat of solution (J·g⁻¹) of a material constituting the resistance layer, C_m—L: a specific heat (J·g⁻¹·K⁻¹) of a material constituting the resistance layer in a liquid state, T_G: a boiling point (° C.) of a material constituting the resistance layer, and Q_L—G: a heat of vaporization (J·g⁻¹) of a material constituting the resistance layer.

17. The cold cathode field emission display according to claim 16, in which the anode electrode is constituted of a set of N anode electrode units (N≧2), and said “C” represents an electrostatic capacity (unit: F) between the focus electrode and the anode electrode unit.

18. A cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions, the anode panel comprising a substrate, a phosphor layer formed on the substrate and an anode electrode formed on the phosphor layer, each cold cathode field emission device comprising: (A) a cathode electrode being formed on a supporting member and extending in a first direction, (B) an insulating layer formed on the supporting member and the cathode electrode, (C) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (D) an insulating film formed on the gate electrode and the insulating layer, (E) a focus electrode formed on the insulating film, (F) a resistance layer for controlling a discharge current, the resistance layer being formed on the focus electrode and having a thickness of t_R (unit: μm), (G) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and (H) an electron-emitting portion exposed in a bottom portion of the opening portion, and the cold cathode field emission display satisfying the following expression (3),
Q>(½)C·V_A² (3) where
Q≈π·t_R·r_R²·d_R×[C_m—S(T_G−T_r)+Q_L—G]×10⁻⁶ and, C: an electrostatic capacity (F) between the focus electrode and the anode electrode, V_A: a voltage (V) to be applied to the anode electrode, r_R: a radius (mm) of a vaporization-allowable region of the resistance layer, d_R: a density (g·cm⁻³) of a material constituting the resistance layer, C_m—S: a specific heat (J·g⁻¹·K⁻¹) of a material constituting the resistance layer in a solid state, T_r: room temperature (° C.), T_G: a boiling point (° C.) of a material constituting the resistance layer, and Q_L—G: a sum (J·g⁻¹) of a heat of vaporization and a heat of solution of a material constituting the resistance layer.

19. The cold cathode field emission display according to claim 18, in which the anode electrode is constituted of a set of N anode electrode units (N≧2), and said “C” represents an electrostatic capacity (unit: F) between the focus electrode and the anode electrode unit.

20. A cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions, the anode panel comprising a substrate, a phosphor layer formed on the substrate and an anode electrode formed on the phosphor layer, each cold cathode field emission device comprising: (A) a cathode electrode being formed on a supporting member and extending in a first direction, (B) an insulating layer formed on the supporting member and the cathode electrode, (C) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction, (D) an insulating film formed on the gate electrode and the insulating layer, (E) a focus electrode formed on the insulating film, (F) a resistance layer for controlling a discharge current, the resistance layer being formed on the focus electrode and having a thickness of t_R (unit: μm), (G) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and (H) an electron-emitting portion exposed in a bottom portion of the opening portion, and the cold cathode field emission display satisfying the following expression (4),
t_R×10⁻²>(½)C·V_A² (4) where C: an electrostatic capacity (F) between the focus electrode and the anode electrode, and V_A: a voltage (V) to be applied to the anode electrode.

21. The cold cathode field emission display according to claim 20, in which the anode electrode is constituted of a set of N anode electrode units (N≧2), and said “C” represents an electrostatic capacity (unit: F) between the focus electrode and the anode electrode unit.

TECHNICAL FIELD

The present invention relates to a cold cathode field emission display characterized in an anode electrode formed in an anode panel or a focus electrode provided in a cold cathode field emission device formed on a cathode panel.

BACKGROUND ART

In the fields of displays for use in television receivers and information terminals, studies have been made for replacing conventional mainstream cathode ray tubes (CRT) with flat-panel displays which are to comply with demands for a decrease in thickness, a decrease in weight, a larger screen and a high fineness. Such flat panel displays include a liquid crystal display (LCD), an electroluminescence display (ELD), a plasma display panel (PDP) and a cold cathode field emission display (FED). Of these, a liquid crystal display is widely used as a display for an information terminal. For applying the liquid crystal display to a floor-type television receiver, however, it still has problems to be solved concerning a higher brightness and an increase in size. In contrast, a cold cathode field emission display (to be sometimes referred to as “display” hereinafter) uses cold cathode field emission devices (to be sometimes referred to as “field emission device” hereinafter) capable of emitting electrons from a solid into a vacuum on the basis of a quantum tunnel effect without relying on thermal excitation, and it is of great interest from the viewpoints of a high brightness and a low power consumption.

As one example of the above field emission device, FIG. 26 shows a schematic partial end view of a filed emission device as shown in FIG. 2 to JP-A-9-90898.

In this field emission device, an insulating layer 2 is deposited on a substrate 1 , and a control electrode (gate electrode) 3 made of a metal thin film is stacked on the insulating layer 2 . A single cavity (opening portion) or a plurality of cavities (opening portions) is/are formed in the insulating layer 2 and the control electrode 3 , and an emitter (electron emitting portion) 4 having the form of a cone is formed therein. An insulating layer 5 and a focus electrode 6 are stacked on the control electrode 3 excluding vicinities of the emitter 4 . The substrate 1 , the insulating layer 2 , the control electrode 3 , the emitter 4 , the insulating layer 5 and the focus electrode 6 constitute a micro cold cathode (field emission device) 7 , and a single micro cold cathode or a plurality of micro cold cathodes constitutes or constitute a cold cathode 15 . In effect, electron beams 8 emitted from the emitter (electron emitting portion) 4 collide with an anode (anode electrode) 9 , and flow in an anode-electrode power source (anode-electrode control circuit) 10 that generates positive voltage.

A voltage to be applied to the control electrode (gate electrode) 3 is generated in a control-electrode power source (gate-electrode control circuit) 17 , and a voltage obtained by potential-dividing the voltage to be applied to the control electrode 3 with a variable resistor is applied to the focus electrode 6 . As a result, the ratio of the voltage of the control electrode 3 and the voltage of the focus electrode 6 is constantly maintained at a value set with the variable resistor 14 . When the focus state in a certain beam current quantity is adjusted with the variable resistor 14 , a nearly equivalent focus state is maintained even if the electron beam current set value taken out from the emitter 4 is changed with an output voltage of the control electrode power source 17 .

Meanwhile, in such a display, the distance between the anode (anode electrode) 9 and the focus electrode 6 is approximately 1 mm at the largest, and an abnormal discharge (vacuum arc discharge) is likely to occur between the anode 9 and the focus electrode 6 . When an abnormal discharge occurs, the voltage of the focus electrode 6 or the control electrode (gate electrode) 3 abnormally increases, so that display performance is impaired in display quality, and further that the field emission device (control electrode 3 , emitter 4 ), the focus electrode 6 and the anode (anode electrode) 9 may be damaged.

In a mechanism in which a discharge takes place in a vacuum space, first, electrons and ions that are emitted from the field emission device under a strong electric field work as a trigger to cause a small-scaled discharge. And, energy is supplied to the anode electrode 9 from the anode-electrode power source (anode-electrode control circuit) 10 , the anode electrode 9 is locally temperature-increased, and an occluded gas inside the anode electrode 9 is released, or a material constituting the anode electrode 9 is caused to vaporize, so that the small-scaled discharge presumably grows to be an abnormal discharge. Besides the anode-electrode power source (anode-electrode control circuit) 10 , energy accumulated in an electrostatic capacity formed between the anode electrode 9 and the field emission device may possibly work as a source for supplying energy that promotes the growth to the abnormal discharge.

For inhibiting the abnormal discharge (vacuum arc discharge), it is effective to control the emission of electrons and ions which trigger the discharge, while it is required to control the particles extremely strictly therefor. In a general production process of the cathode panels or the anode panels or the display panels using the anode panels or the cathode panels, practicing the above control involves great technical difficulties.

It is therefore an object of the present invention to provide a cold cathode field emission display that is so structured to be capable of inhibiting the occurrence of critical damage caused by energy, which is generated by an electrostatic capacity between the anode electrode and the field emission device, on an anode electrode or an electrode constituting the cold cathode field emission device even when a discharge takes place between the electrode constituting the cold cathode field emission device and the anode electrode.

DISCLOSURE OF THE INVENTION

The cold cathode field emission display according to a first aspect of the present invention for achieving the above object is a cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions,

the anode panel comprising a substrate, a phosphor layer formed on the substrate, an anode electrode formed on the phosphor layer and a resistance layer for controlling a discharge current, the resistance layer being formed on the anode electrode and having a thickness of t _R (unit: μm), and

the cold cathode field emission display satisfying the following expression (1).
Q >(½) C·V _A ² (1)

The cold cathode field emission display according to a second aspect of the present invention for achieving the above object is a cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions,

the anode panel comprising a substrate, a phosphor layer formed on the substrate, an anode electrode formed on the phosphor layer and a resistance layer for controlling a discharge current, the resistance layer being formed on the anode electrode and having a thickness of t _R (unit: μm), and

the cold cathode field emission display satisfying the following expression (2).
t _R ×10 ⁻² >(½) C·V _A ² (2)

The cold cathode field emission display according to the first or second aspect of the present invention may have a constitution that each cold cathode field emission device comprises:

• (a) a cathode electrode being formed on the supporting member and extending in a first direction,
• (b) an insulating layer formed on the supporting member and the cathode electrode,
• (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction,
• (d) an insulating film formed on the gate electrode and the insulating layer,
• (e) a focus electrode formed on the insulating film,
• (f) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and
• (g) an electron-emitting portion exposed in a bottom portion of the opening portion.

In this case, each cold cathode field emission device may have a constitution further comprising:

• (h) a second resistance layer for controlling a discharge current, the second resistance layer being formed on the focus electrode and having a thickness of t′ _R (unit: μm). In this case, the cold cathode field emission display according to the first aspect of the present invention preferably satisfies
  Q ′=(½) C′·V _A ² (1′)
  and the cold cathode field emission display according to the second aspect of the present invention preferably satisfies
  t′ _R ×10 ⁻² >(½) C′·V _A ² (2′).

Alternatively, the cold cathode field emission display according to the first or second aspect of the present invention may have a constitution that each cold cathode field emission device comprises:

• (a) a cathode electrode being formed on a supporting member and extending in a first direction,
• (b) an insulating layer formed on the supporting member and the cathode electrode,
• (c) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction,
• (d) an opening portion formed through the gate electrode and the insulating layer, and
• (e) an electron-emitting portion exposed in a bottom portion of the opening portion.

The cold cathode field emission display according to a third aspect of the present invention for achieving the above object is a cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions,

the anode panel comprising a substrate, a phosphor layer formed on the substrate and an anode electrode formed on the phosphor layer,

each cold cathode field emission device comprising:

• (A) a cathode electrode being formed on a supporting member and extending in a first direction,
• (B) an insulating layer formed on the supporting member and the cathode electrode,
• (C) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction,
• (D) an insulating film formed on the gate electrode and the insulating layer,
• (E) a focus electrode formed on the insulating film,
• (F) a resistance layer for controlling a discharge current, the resistance layer being formed on the focus electrode and having a thickness of t _R (unit: μm),
• (G) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and
• (H) an electron-emitting portion exposed in a bottom portion of the opening portion, and

the cold cathode field emission display satisfying the following expression (3).
Q >(½) C·V _A ² (3)

The cold cathode field emission display according to a fourth aspect of the present invention for achieving the above object is a cold cathode field emission display comprising a cathode panel having a plurality of cold cathode field emission devices and an anode panel which panels are bonded to each other in their circumferential portions,

the anode panel comprising a substrate, a phosphor layer formed on the substrate and an anode electrode formed on the phosphor layer,

each cold cathode field emission device comprising:

• (A) a cathode electrode being formed on a supporting member and extending in a first direction,
• (B) an insulating layer formed on the supporting member and the cathode electrode,
• (C) a gate electrode being formed on the insulating layer and extending in a second direction different from the first direction,
• (D) an insulating film formed on the gate electrode and the insulating layer,
• (E) a focus electrode formed on the insulating film,
• (F) a resistance layer for controlling a discharge current, the resistance layer being formed on the focus electrode and having a thickness of t _R (unit: μm),
• (G) an opening portion formed through the focus electrode, the insulating film, the gate electrode and the insulating layer, and
• (H) an electron-emitting portion exposed in a bottom portion of the opening portion, and the cold cathode field emission display satisfying the following expression (4).
  t _R ×10 ⁻² >(½) C·V _A ² (4)

In the cold cathode field emission display according to the first or third aspect of the present invention, when a material constituting the resistance layer vaporizes from a solid phase through a liquid phase, the following expression is given.

$Q\approx \pi ·t_R·r_R^2·d_R\times \left[C_{\mathrm{m\_S}}\left(T_L-T_r\right)+Q_{\mathrm{S\_L}}+C_{\mathrm{m\_L}}\left(T_G-T_L\right)+Q_{\mathrm{L\_G}}\right]\times {10}^{-6}$

In the cold cathode field emission display according to the first or third aspect of the present invention, when a material constituting the resistance layer vaporizes from a solid phase directly, the following expression is given.
Q≈π·t _R ·r _R ² ·d _R ×[C _{m — S} ( T _G −T _r )+ Q _{L — G} ]×10 ⁻⁶

In the cold cathode field emission display according to any one of the first to fourth aspects of the present invention, V _A is a voltage (V) to be applied to the anode electrode.

In the expressions (1) to (4), rigorously, V _A represents a voltage difference between a voltage to be applied to the anode electrode and a voltage to be applied to that electrode (for example, a focus electrode) of the cold cathode field emission device which is opposed to the anode electrode. Since, however, the voltage to be applied to the anode electrode is sufficiently high as compared with the voltage to be applied to that electrode (for example, a focus electrode) of the cold cathode field emission device which is opposed to the anode electrode, it is determined that V _A on the right-hand side of each of the expressions (1) to (4) is a voltage to be applied to the anode electrode.

In the cold cathode field emission display according to the first or second aspect of the present invention, “C” represents an electrostatic capacity (F) between the cold cathode field emission device and the anode electrode. In the cold cathode field emission display according to the third or fourth aspect of the present invention, “C” represents an electric capacity (F) between the focus electrode and the anode electrode. In a preferred embodiment according to the first aspect of the present invention, “C′” represents an electrostatic capacity (F) between the focus electrode and the anode electrode.

In the cold cathode field emission display according to the first or third aspect of the present invention, further,

• r _R : a radius (mm) of a vaporization-allowable region of the resistance layer,
• d _R : a density (g·cm ⁻³ ) of a material constituting the resistance layer,
• C _{m — S} : a specific heat (J·g ⁻¹ ·K ⁻¹ ) of a material constituting the resistance layer in a solid state,
• T _L : a melting point (° C.) of a material constituting the resistance layer,
• T _r : room temperature (° C.),
• Q _{S — L} : a heat of solution (J·g ⁻¹ ) of a material constituting the resistance layer,
• C _{m — L} : a specific heat (J·g ⁻¹ ·K ⁻¹ ) of a material constituting the resistance layer in a liquid state,
• T _G : a boiling point (° C.) of a material constituting the resistance layer.

Further, when the material constituting the resistance layer vaporizes from a solid phase through a liquid phase,

• Q _{L — G} : a heat of vaporization (J·g ⁻¹ ) of a material constituting a resistance layer.

When a material constituting the resistance layer vaporizes from a solid phase directly,

• Q _{L — G} : a sum (J·g ⁻¹ ) of a heat of vaporization and a heat of solution of a material constituting the resistance layer.

In a preferred embodiment according to the first aspect of the present invention, when a material constituting the second resistance layer vaporizes from a solid phase through a liquid phase, the following expression is given.

$Q^{\prime }\approx \pi ·t_R^{\prime }·r_R^{\mathrm{\prime 2}}·d_R^{\prime }\times \left[C_{\mathrm{m\_S}}^{\prime }\left(T_L^{\prime }-T_r\right)+Q_{\mathrm{S\_L}}^{\prime }+C_{\mathrm{m\_L}}^{\prime }\left(T_G^{\prime }-T_L^{\prime }\right)+Q_{\mathrm{L\_G}}^{\prime }\right]\times {10}^{-6}$

Alternatively, in a preferred embodiment according to the first aspect of the present invention, when a material constituting the second resistance layer vaporizes from a solid phase directly, the following expression is given.

$Q^{\prime }\approx \pi ·t_R^{\prime }·r_R^{\mathrm{\prime 2}}·d_R^{\prime }\times \left[C_{\mathrm{m\_S}}^{\prime }\left(T_G^{\prime }-T_r\right)+Q_{\mathrm{L\_G}}^{\prime }\right]\times {10}^{-6}$

In the above expression,

• r′ _R : a radius (mm) of a vaporization-allowable region of the second resistance layer,
• d′ _R : a density (g·cm ⁻³ ) of a material constituting the second resistance layer,
• C′ _{m — S} : a specific heat (J·g ⁻¹ ·K ⁻¹ ) of a material constituting the second resistance layer in a solid state,
• T′ _L : a melting point (° C.) of a material constituting the second resistance layer,
• T _r : room temperature (° C.),
• Q′ _{S — L} : a heat of solution (J·g ⁻¹ ) of a material constituting the second resistance layer,
• C′ _{m — L} : a specific heat (J·g ⁻¹ ·K ⁻¹ ) of a material constituting the second resistance layer in a liquid state,
• T′ _G : a boiling point (° C.) of a material constituting the second resistance layer.

Further, when a material constituting the second resistance layer vaporizes from a solid phase through a liquid phase,

• Q′ _{L — G} : a heat of vaporization (J·g ⁻¹ ) of a material constituting the second resistance layer.

When a material constituting the second resistance layer vaporizes from a solid phase directly,

• Q′ _{L — G} : a sum (J·g ⁻¹ ) of a heat of solution and a heat of vaporization of a material constituting the second resistance layer.

The electrostatic capacity “C” between the cold cathode field emission device and the anode electrode can be measured as follows. When the cold cathode field emission device comprises a cathode electrode and a gate electrode, all of gate electrodes are short-circuited and an electrostatic capacity between such a short-circuited gate electrode and the anode electrode is measured by a known method. When the cold cathode field emission device comprises a cathode electrode, a gate electrode and a focus electrode, an electrostatic capacity between the focus electrode and the anode electrode is measured by a known method.

The vaporization-allowable region of the resistance layer or the second resistance layer does not have any circular form, the radius of a circle having the same area as that of the region can be regarded as r _R or r′ _R .

In the cold cathode field emission device provided in the the cold cathode field emission display according to any one of the first to fourth aspects of the present invention including the preferred embodiments (these will be sometimes referred to as “the display of the present invention” hereinafter), preferably, the cathode electrode and the gate electrode have the form of a stripe, and the projection image of the cathode electrode and the projection image of the gate electrode cross each other at right angles in view of the simplification of structure of the cold cathode field emission display.

In the display of the present invention, desirably, the focus electrode has the form of one sheet that covers an effective field (a region to function as an actual display portion). An opening portion is formed in the focus electrode for passing electrons emitted from an electron-emitting region or an electron-emitting portion through the focus electrode. The above opening portion may be provided in each cold cathode field emission device, or may be provided in each electron-emitting region (each overlap region). The electron-emitting region is constituted of a single or a plurality of electron-emitting portions, which constitutes the electron emission device, formed in a region (an overlap region) where a projection image of the cathode electrode and a projection image of the gate electrode overlap.

In the display of the present invention, the anode electrode may have a constitution having the form of one sheet that covers the effective field, or may be constituted of a set of N anode electrode units (N≧2). In the latter case, the above “C” represents an electrostatic capacity (unit: F) between the cold cathode field emission device or the focus electrode and the anode electrode unit. In the anode electrode unit, for example, when the total number of columns of unit phosphor layers (phosphor layers that generate one bright spot in a display) that are arranged in the form of a straight line and constitute one subpixel is n, there may be employed a constitution in which N=n, there may be employed another constitution in which n=α·N (α is an integer of 2 or more, preferably 10≦α≦100, more preferably 20≦α≦50), or the number N may be a number obtained by adding 1 to the number of spacers (to be described later) provided at regular intervals. The size of each of the anode electrode units may be constant regardless of their positions or may be different depending upon their positions.

When the distance between the anode electrode unit and the cold cathode field emission device is “L” (unit: mm) and when the anode electrode unit has an area S _AU (unit: mm ² ), preferably, (V _A /7) ² ×(S _AU /L)≦2250 is satisfied, more preferably, (V _A /7) ² ×(S _AU /L)≦450 is satisfied, for preventing the scale-up of damage caused on the anode electrode unit, such as melting of the anode electrode unit, due to a discharge between the anode electrode unit and the cold cathode field emission device. When a convexoconcave shape exists in the anode electrode unit and when the distance “L” between the anode electrode unit and the cold cathode field emission device is not constant, the shortest distance between the anode electrode unit and the cold cathode field emission device is taken as “L”.

In the display of the present invention, the material for constituting the resistance layer includes carbon materials such as silicon carbide (SiC) and SiCN; SiN; refractory metal oxides such as ruthenium oxide (RuO ₂ ), tantalum oxide, tantalum oxide, chromium oxide and titanium oxide; semiconductor materials such as amorphous silicon; and ITO. The resistance layer can be formed by a PVD method such as a vapor deposition method and a sputtering method; or a CVD method.

Examples of the cold cathode field emission device (to be abbreviated as “field emission device” hereinafter) include:

• (1) a Spindt-type field emission device (field emission device in which a conical electron-emitting portion is formed on the cathode electrode positioned in the bottom portion of the opening portion),
• (2) a plane-type field emission device (field emission device in which a nearly plane-surface-shaped electron-emitting portion is formed on the cathode electrode positioned in the bottom portion of the opening portion),
• (3) a crown-type field emission device (field emission device in which a crown-shaped electron-emitting portion is formed on the cathode electrode positioned in the bottom portion of the opening portion),
• (4) a flat-type field emission device that emits electrons from the surface of the flat cathode electrode,
• (5) a crater-type field emission device that emits electrons from convex portions of surface of the cathode electrode having a convexoconcave shape formed on the surface, and
• (6) an edge-type field emission device that emits electrons from an edge portion of the cathode electrode.

In addition to the above-mentioned forms of the field emission device, a device generally called a surface-conduction-type electron emitting device is known as the field emission device and can be applied to the cold cathode field emission display of the present invention. In the surface-conduction-type electron emitting device, thin films composed of material such as tin oxide (SnO ₂ ), gold (Au), indium oxide (In ₂ O ₃ )/tin oxide (SnO ₂ ), carbon, palladium oxide (PdO) or the like and having a very small area are formed in the form of a matrix on the substrate made, for example, of glass. Each thin film is constituted of a pair of thin film fragments and has a constitution in which a wiring in the row direction is connected to one of each pair of the thin film fragments and a wiring in the column direction is connected to the other of each pair of the thin film fragments and a several nm gap is formed between one of each pair of the thin film fragments and the other of each pair of the thin film fragments. In the thin film selected by the wiring in the row direction and the wiring in the column direction, electrons are emitted from the thin film through the gap.

In the display of the present invention, the substrate for constituting the anode panel includes a glass substrate, a glass substrate having an insulating film formed on its surface, a quartz substrate, a quartz substrate having an insulating film formed on its surface and a semiconductor substrate having an insulating film formed on its surface. From the viewpoint that the production cost is decreased, it is preferred to use a glass substrate or a glass substrate having an insulating film formed on its surface. Examples of the glass substrate include high-distortion glass, soda glass (Na ₂ O.CaO.SiO ₂ ), borosilicate glass (Na ₂ O.B ₂ O ₃ .SiO ₂ ), forsterite (2MgO.SiO ₂ ) and lead glass (Na ₂ O.PbO.SiO ₂ ). A supporting member for constituting the cathode panel can have the same constitution as that of the above substrate.

The material for constituting the cathode electrode, the gate electrode or the focus electrode includes metals such as aluminum (Al), tungsten (W), niobium (Nb), tantalum (Ta), molybdenum (Mo), chromium (Cr), copper (Cu), gold (Au), silver (Ag), titanium (Ti), nickel (Ni) and the like; alloys or compounds containing these metal elements (for example, nitrides such as TiN and silicides such as WSi ₂ , MoSi ₂ , TiSi ₂ and TaSi ₂ ); electrically conductive metal oxides such as ITO (indium-tin oxide), indium oxide and zinc oxide; and semiconductors such as silicon (Si). For making or forming the cathode electrode, the gate electrode or the focus electrode, a thin film made of the above material is formed on a substratum by a known thin film forming method such as a CVD method, a sputtering method, a vapor deposition method, an ion-plating method, an electrolytic plating method, an electroless plating method, a screen printing method, a laser abrasion method or a sol-gel method. When the thin film is formed on the entire surface of the substratum, the thin film is patterned by a known patterning method to form the above members. When a patterned resist is formed on the substratum in advance of the formation of the thin film, the above members can be formed by a lift-off method. Further, when vapor deposition is carried out using a mask having openings conforming to the cathode electrode or the gate electrode, or when screen printing is carried out with a screen having such openings, no patterning is required after the formation of the thin film.

As a material for constituting the insulating layer or the insulating film which constitutes the field emission device, SiO ₂ -containing material such as SiO ₂ , BPSG, PSG, BSG, AsSG, PbSG, SiN, SiON, spin on glass (SOG), low-melting-point glass and a glass paste; SiN; an insulating resin such as polyimide and the like can be used alone or in combination. The insulating layer or the insulating film can be formed by a known method such as a CVD method, an application method, a sputtering method or a screen printing method.

The electron-emitting portion will be explained in detail later.

Examples of a material for constituting the anode electrode include aluminum (Al) and chromium (Cr). When the anode electrode is made of aluminum (Al) or chromium (Cr), for example, the specific thickness of the anode electrode is 3×10 ⁻⁸ m (30 nm) to 1.5×10 ⁻⁷ m (150 nm), preferably 5×10 ⁻⁸ m (50 nm) to 1×10 ⁻⁷ m (100 nm). The anode electrode can be formed by a vapor deposition method or a sputtering method.

The phosphor layer may be made of monochromatic phosphor particles, or it may be made of phosphor particles of three primary colors. Further, the arrangement form of the phosphor layer may be a dot matrix form, or it may be a stripe form. In the arrangement form such as a dot matrix form or a stripe form, a black matrix for improvement in contrast may be embedded in a space between one phosphor layer and another adjacent phosphor layer.

Further, the anode panel is preferably provided with a plurality of separation walls for preventing the occurrence of a so-called optical crosstalk (color mixing) that is caused when electrons recoiling from the phosphor layer or secondary electrons emitted from the phosphor layer enter another phosphor layer, or for preventing the collision of electrons with other phosphor layer when electrons recoiling from the phosphor layer or secondary electrons emitted from the phosphor layer enter other phosphor layer over the separation wall.

The form of the separation walls includes the form of a lattice (grilles), that is, a form in which the separation wall surrounds four sides of the phosphor layer corresponding to one pixel and having a plan form of nearly a rectangle (or dot-shaped), and a stripe or band-like form that extends in parallel with opposite two sides of a rectangular or stripe-shaped phosphor layer. When the separation wall(s) has(have) the form of a lattice, the separation wall may have a form in which the separation wall continuously or discontinuously surrounds four sides of one phosphor layer. When the separation wall(s) has(have) the form of a stripe or band-like form, the form may be continuous or discontinuous. The formed separation walls may be polished to flatten the top surface of each separation wall.

For improving the contrast of display images, preferably, a black matrix that absorbs light from the phosphor layer is formed between one phosphor layer and another adjacent phosphor layer and between the separation wall and the substrate. As a material for constituting the black matrix, it is preferred to select a material that absorbs at least 99% of light from the phosphor layer. The above material includes carbon, a thin metal film (made, for example, of chromium, nickel, aluminum, molybdenum and an alloy of these), a metal oxide (for example, chromium oxide), metal nitride (for example, chromium nitride), a heat-resistant organic resin, glass paste, and glass paste containing a black pigment or electrically conductive particles of silver or the like. Specific examples thereof include a photosensitive polyimide resin, chromium oxide, and a chromium oxide/chromium stacked film. Concerning the chromium oxide/chromium stacked film, the chromium film is to be in contact with the substrate.

When the cathode panel and the anode panel are bonded in their circumferential portions, the bonding may be carried out with an adhesive layer or with a frame made of an insulating rigid material such as glass or ceramic and an adhesive layer. When the frame and the adhesive layer are used in combination, the facing distance between the cathode panel and the anode panel can be adjusted to be longer by properly determining the height of the frame than that obtained when the adhesive layer alone is used. While a frit glass is generally used as a material for the adhesive layer, a so-called low-melting-point metal material having a melting point of approximately 120 to 400° C. may be used. The low-melting-point metal material includes In (indium; melting point 157° C.); an indium-gold low-melting-point alloy; tin (Sn)-containing high-temperature solders such as Sn ₈₀ Ag ₂₀ (melting point 220 to 370° C.) and Sn ₉₅ Cu ₅ (melting point 227 to 370° C.); lead (Pb)-containing high-temperature solders such as Pb _97.5 Ag _2.5 (melting point 304° C.), Pb _94.5 Ag _5.5 (melting point 304 to 365° C.) and Pb _97.5 Ag _1.5 Sn _1.0 (melting point 309° C.); zinc (Zn)-containing high-temperature solders such as Zn ₉₅ Al ₅ (melting point 380° C.); tin-lead-containing standard solders such as Sn ₅ Pb ₉₅ (melting point 300 to 314° C.) and Sn ₂ Pb ₉₈ (melting point 316 to 322° C.); and brazing materials such as Au ₈₈ Ga ₁₂ (melting point 381° C.) (all of the above parenthesized values show atomic %).

When three members of the substrate, the supporting member and the frame are bonded, these three members may be bonded at the same time, or one of the substrate and the supporting member may be bonded to the frame at a first stage, and then the other of the substrate and the supporting member may be bonded to the frame at a second stage. When bonding of the three members or bonding at the second stage is carried out in a high-vacuum atmosphere, a space surrounded by the substrate, the supporting member, the frame and the adhesive layer comes to be a vacuum space upon bonding. Otherwise, after the three members are bonded, the space surrounded by the substrate, the supporting member, the frame and the adhesive layer may be vacuumed to obtain a vacuum space. When the vacuuming is carried out after the bonding, the pressure in an atmosphere during the bonding may be any one of atmospheric pressure and reduced pressure, and the gas constituting the atmosphere may be ambient atmosphere or an inert gas containing nitrogen gas or a gas (for example, Ar gas) coming under the group 0 of the periodic table.

When the vacuuming is carried out after the bonding, the vacuuming can be carried out through a tip tube pre-connected to the substrate and/or the supporting member. Typically, the tip tube is made of a glass tube and is bonded to a circumference of a through-hole formed in an ineffective field of the substrate and/or the supporting member (i.e., the field other than the effective field which works as a display portion) with a frit glass or the above low-melting-point metal material. After the space reaches a predetermined degree of vacuum, the tip tube is sealed by thermal fusion. It is preferred to heat and then temperature-decrease the cold cathode field emission display as a whole before the sealing, since residual gas can be released into the space, and the residual gas can be removed out of the space by vacuuming.

The display is internally in a high vacuum state, and atmospheric pressure is exerted on the display. The display is therefore preferably internally provided with spacers for preventing atmospheric pressure from damaging the display. Examples of a material for constituting the spacer include glass and ceramics (for example, a ceramic obtained by adding titanium oxide, chromium oxide, iron oxide, vanadium oxide or nickel oxide to mullite, alumina, barium titanate, lead titanate zirconate, zirconia, cordierite, barium borosilicate, iron silicate or a glass ceramic material). The spacer can be fixed to the anode panel, for example, with a spacer holder formed in the anode panel or partition walls.

In the display of the present invention, the cathode electrode is connected to a cathode-electrode control circuit, the gate electrode is connected to a gate-electrode control circuit, the anode electrode is connected to an anode-electrode control circuit, and the focus electrode is connected to the focus-electrode control circuit. These control circuits can be constituted of known circuits. The output voltage V _A of the anode-electrode control circuit is generally constant, and it can be set, for example, at 5 kilovolts to 10 kilovolts. Concerning the voltage V _C to be applied to the cathode electrode and the voltage V _G to be applied to the gate electrode, there can be employed (1) a method in which the voltage V _C to be applied to the cathode electrode is set at a constant level and the voltage V _G to be applied to the gate electrode is changed, (2) a method in which the voltage V _C to be applied to the cathode electrode is changed and the voltage V _G to be applied to the gate electrode is set at a constant level, or (3) a method in which the voltage V _C to be applied to the cathode electrode is changed and the voltage V _G to be applied to the gate electrode is also changed. A constant voltage of 0 volt or approximately −20 volts at maximum is applied to the focus electrode from the focus-electrode control circuit.

In the cold cathode field emission display of the present invention, the relationship of the total energy “Q” required for the vaporization of the resistance layer, the electrostatic capacity “C” between the cold cathode field emission device or the focus electrode and the anode electrode and the voltage V _A to be applied to the anode electrode are defined, so that the occurrence of damage, caused by energy generated on basis of an electrostatic capacity formed between the anode electrode and the field emission device, on members constituting the resistance layer, the anode electrode or the cold cathode field emission device can be reliably suppressed even when a discharge takes place between the cold cathode field emission device or the focus electrode and the anode electrode. Alternatively, the relationship of the thickness t _R of the resistance layer, the electrostatic capacity “C” between the cold cathode field emission device or the focus electrode and the anode electrode and the voltage V _A to be applied to the anode electrode are defined, so that the occurrence of damage, caused by energy generated on the basis of an electrostatic capacity formed between the anode electrode and the field emission device, on members constituting the resistance layer, the anode electrode and the cold cathode field emission device can be reliably suppressed even when a discharge takes place between the cold cathode field emission device or the focus electrode and the anode electrode. Further, the resistance layer is provided, so that the peak value of a discharge current can be decreased.

Further, when the anode electrode has a form in which the anode electrode is divided into the anode electrode units having smaller areas in place of forming the anode electrode on the entire region of the effective field, the electrostatic capacity between the cold cathode field emission device or the focus electrode and the anode electrode unit can be decreased, so that the thickness of the resistance layer can be consequently decreased. Further, the energy generated on the basis of the electrostatic capacity formed between the anode electrode and the field emission device can be decreased, so that extent of the damage caused on the anode electrode by a discharge can be further decreased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic partial end view of a cold cathode field emission display of Example 1.

FIG. 2 is a schematic partial perspective view obtained when a cathode panel CP and an anode panel AP constituting the cold cathode field emission display of Example 1 are disassembled.

FIG. 3 is a schematic layout drawing that shows a layout of partition walls, spacers and phosphor layers in the anode panel constituting a cold cathode field emission display.

FIG. 4 is a schematic layout drawing that shows a layout of partition walls, spacers and phosphor layers in the anode panel constituting a cold cathode field emission display.

FIG. 5 is a schematic layout drawing that shows a layout of partition walls, spacers and phosphor layers in the anode panel constituting a cold cathode field emission display.

FIG. 6 is a schematic layout drawing that shows a layout of partition walls, spacers and phosphor layers in the anode panel constituting a cold cathode field emission display.

FIG. 7 is a schematic showing of a discharge state when a resistance layer is formed in a discharge current path in the cold cathode field emission display of Example 1.

FIG. 8 is an equivalent circuit found when a discharge takes place between the anode electrode and the focus electrode in the cold cathode field emission display of Example 1.

FIG. 9 is a graph showing a calculation result with regard to a discharge current when the electric resistance value “R” of a resistance layer for controlling a discharge current in the equivalent circuit shown in FIG. 8 is set at 0.9Ω.

FIG. 10 is a schematic partial end view of a cold cathode field emission display of Example 2.

FIG. 11 is a schematic partial end view of a cold cathode field emission display of Example 3.

FIG. 12 is a schematic plan view of an anode electrode in a cold cathode field emission display of Example 4.

FIGS. 13A and 13B are a schematic partial end view of an anode panel taken along line A-A in FIG. 12 and a schematic partial end view of the same taken along line B-B in FIG. 12, respectively.

FIG. 14 is an equivalent circuit found when a discharge takes place between an anode electrode unit and a focus electrode in the cold cathode field emission display of Example 4 having no resistance layer.

FIG. 15 is a graph showing simulation results with regard to a change in abnormal discharge current “i” when the anode electrode unit of the cold cathode field emission display of Example 4 has an area S _AU of 9000 mm ² , 3000 mm ² and 450 mm ² .

FIG. 16 is a graph showing simulation results with regard to an integration value of energy generated during an abnormal discharge when the anode electrode unit of the cold cathode field emission display of Example 4 has an area S _AU of 9000 mm ² , 3000 mm ² and 450 mm ² .

FIGS. 17A and 17B are schematic partial end views of a supporting member, etc., for explaining a method of manufacturing a Spindt-type cold cathode field emission device.

FIGS. 18A and 18B, following FIG. 17B, are schematic partial end views of the supporting member, etc., for explaining a method of manufacturing the Spindt-type cold cathode field emission device.

FIGS. 19A and 19B are schematic partial cross-sectional views of a supporting member, etc., for explaining a method of manufacturing a plane-type cold cathode field emission device (No. 1).

FIGS. 20A and 20B, following FIG. 19B, are schematic partial cross-sectional views of a supporting member, etc., for explaining the method of manufacturing the plane-type cold cathode field emission device (No. 1).

FIGS. 21A and 21B are a schematic partial cross-sectional view of a plane-type cold cathode field emission device (No. 2) and a schematic partial cross-sectional view of a flat-type cold cathode field emission device, respectively.

FIGS. 22A to 22F are schematic partial cross-sectional views of a substrate, etc., for explaining a method of manufacturing an anode panel.

FIG. 23 is a schematic partial end view of a variant of the cold cathode field emission display.

FIG. 24 is a schematic partial end view of another variant of the cold cathode field emission display.

FIG. 25 is a schematic showing of a layout state of a focus electrode, an opening portion formed through the focus electrode and an opening portion formed through the gate electrode in another variant of the cold cathode field emission display shown in FIG. 24, FIG. 25 being drawn by viewing the electron-emitting region from above.

FIG. 26 is a schematic partial end view of a field emission device disclosed in FIG. 2 to JP-A-9-90898.

FIG. 27 is an equivalent circuit found when a discharge takes place between an anode electrode and a focus electrode when no resistance layer is formed.

FIG. 28 is a graph showing results with regard to a discharge current calculated when R _A =100 kΩ in the equivalent circuit shown in FIG. 27.

FIG. 29 is a graph showing results with regard to a discharge current calculated when R _A =1 kΩ in the equivalent circuit shown in FIG. 27.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained hereinafter with reference to Examples by referring to drawings.

EXAMPLE 1

Example 1 is directed to the cold cathode field emission display (to be simply abbreviated as “display” hereinafter) according to the first and second aspects of the present invention.

FIG. 1 shows a schematic partial end view of the display of Example 1, and FIG. 2 shows a schematic partial perspective view found when a cathode panel CP and an anode panel AP are disassembled. FIG. 1 omits showing of spacers, and FIG. 2 omits showing of partition walls, spacers and a resistance layer and also omits showing of a focus electrode and an insulating layer.

In the display of Example 1, a cathode panel CP having a plurality of cold cathode field emission devices (to be referred to as “field emission devices” hereinafter) having a cathode electrode 11 , a gate electrode 13 , a focus electrode 15 and an electron-emitting portion 17 and an anode panel AP are bonded to each other through a frame 40 in their circumferential portions.

The anode panel comprises a substrate 30 , a phosphor layer 31 (red-light-emitting phosphor layer 31 R, green-light-emitting phosphor layer 31 G and blue-light-emitting phosphor layer 31 B) formed on the substrate 30 , an anode electrode 35 formed on the phosphor layer 31 and a resistance layer 36 for controlling a discharge current, the resistance layer 36 being formed on the anode electrode 35 and having a thickness of t _R (unit: μm). The above anode electrode 35 is made of an aluminum thin film and has the form of one sheet covering an effective field. Further, the resistance layer 36 is made of ITO having a thickness t _R of 0.2 μm and is formed on the entire area of the anode electrode 35 .

A black matrix 32 is formed on the substrate 30 between one phosphor layer 31 and another phosphor layer 31 . A separation wall 33 is formed on the black matrix 32 . FIGS. 3 to 6 schematically show examples of layout of the separation walls 33 , spacer 34 and the phosphor layers 31 in the anode panel AP. The plan form of the separation wall 33 includes the form of a lattice (grid form), i.e., a form that surrounds the phosphor layer 31 having the plan form, for example, of a nearly rectangle and equivalent to one sub pixel (see FIGS. 3 and 4), and a form of a band (stripe form) extending in parallel with facing two sides of the phosphor layer 31 having a nearly rectangular form (or strip form) (see FIGS. 5 and 6). The phosphor layer 31 may have the form of a stripe that extends vertically on FIGS. 3 to 6. Part of the separation wall 33 works as a spacer holding portion for holding the spacer 34 .

The field emission device shown in FIG. 1 is a so-called Spindt-type field emission device having a conical electron-emitting portion. This field emission device comprises:

• (a) a cathode electrode 11 formed on a supporting member 10 and extending in a first direction,
• (b) an insulating layer 12 formed on the supporting member 10 and the cathode electrode 11 ,
• (c) a gate electrode 13 being formed on the insulating layer 12 and extending in a second direction different from the first direction,
• (d) an insulating film 14 formed on the gate electrode 13 and the insulating layer 12 ,
• (e) a focus electrode 15 formed on the insulating film 14 ,
• (f) an opening portion 16 formed through the focus electrode 15 , the insulating film 14 , the gate electrode 13 and the insulating layer 12 (an opening portion 16 A formed through the focus electrode 15 and the insulating film 14 , an opening portion 16 B formed through the gate electrode 13 , and an opening portion 16 C formed through the insulating layer 12 ), and
• (g) an electron-emitting portion 17 formed on the cathode electrode 11 positioned in the bottom portion of the opening portion.

The electron-emitting portion 17 is constituted, specifically, of a conical electron-emitting portion formed on the cathode electrode 11 positioned in a bottom portion of the opening portion 16 C. Further, the focus electrode 15 has the form of one sheet covering the effective field. The opening portion 16 A formed through the focus electrode 15 is provided for each cold cathode field emission device.

Generally, the cathode electrode 11 and the gate electrode 13 are formed in the form of a stripe each in directions in which the projection images of these two electrodes cross each other at right angles. Generally, a plurality of field emission devices are arranged in a region (corresponding to one pixel, and the region will be called an “overlap region” or an “electron-emitting region” hereinafter) where the projection images of the above two electrodes overlap. Further, generally, such electron-emitting regions are arranged in the form of a two-dimensional matrix within the effective field (which works as an actual display portion) of the cathode panel CP.

The space surrounded by the anode panel AP, the cathode panel CP and a frame 40 is a vacuum space. Atmosphere has a pressure on the anode panel AP and the cathode panel CP. The spacer 34 having a height, for example, of about 1 mm is provided between the anode panel AP and the cathode panel CP for preventing the pressure from destroying the display.

Each picture element (one pixel) is constituted of a group of field emission devices formed in the three overlap regions of the cathode electrode 11 and the gate electrode 13 on the cathode panel side, and the phosphor layer 31 (an aggregate of one unit phosphor layer for emitting light in red 31 R, one unit phosphor layer for emitting light in green 31 G and one unit phosphor layer for emitting light in blue 31 B) that faces three overlap regions and is on the anode panel side. Such pixels are arranged in the effective field on the order of, for example, several hundreds thousand to several millions. Further, each picture element (one pixel) is constituted of three subpixels, each pixel is constituted of a group of the field emission devices formed on the overlap region of the cathode electrode 11 and the gate electrode 13 of the cathode panel side and the phosphor layer 31 (an aggregate of one unit phosphor layer for emitting light in red 31 R, one unit phosphor layer for emitting light in green 31 G and one unit phosphor layer for emitting light in blue 31 B) of the anode panel side arranged so as to face the group of the field emission devices.

The anode panel AP and the cathode panel CP are arranged such that the electron-emitting region and the phosphor layer 31 face each other, and they are bonded to each other in their circumferential portions through the frame 40 , whereby a display can be manufactured. An ineffective field surrounding the effective field and having peripheral circuits for selecting pixels is provided with a through hole (not shown) for vacuuming, and a tip tube (not shown) that is to be sealed after the vacuuming is connected to the through hole. That is, the space surrounded by the anode panel AP, the cathode panel CP and the frame 40 is a vacuum space.

A relatively negative voltage V _c is applied to the cathode electrode 11 from the cathode-electrode control circuit 41 , a relatively positive voltage V _G is applied to the gate electrode 13 from the gate-electrode control circuit 42 , a relatively negative voltage V _F is applied to the focus electrode 15 from the focus-electrode control circuit 43 , and a positive voltage V _A higher than that applied to the gate electrode 13 is applied to the anode electrode 35 from the anode-electrode control circuit 44 . When display is performed with the above display, for example, a scanning signal is inputted to the cathode electrode 11 from the cathode-electrode control circuit 41 , and a video signal is inputted to the gate electrode 13 from the gate-electrode control circuit 42 . Reversely, a video signal may be inputted to the cathode electrode 11 from the cathode-electrode control circuit 41 , and a scanning signal may be inputted to the gate electrode 13 from the gate-electrode control circuit 42 . Due to an electric field generated when a voltage is applied between the cathode electrode 11 and the gate electrode 13 , electrons are emitted from the electron-emitting portion 17 on the basis of a quantum tunnel effect, and the electrons are drawn toward the anode electrode 35 to collide with the phosphor layers 31 . As a result, the phosphor layers 31 are excited, whereby a desired image can be obtained. That is, the operation of the display is basically controlled by the voltage applied to the gate electrode 13 and the voltage applied to the electron-emitting portion 17 through the cathode electrode 11 .

FIG. 27 shows an equivalent circuit found when a discharge takes place between the anode electrode 35 and the focus electrode 15 in a conventional display having no resistance layer 36 .

In this Example, a positive voltage V _A (10 kV) was applied to the anode electrode 35 from the anode-electrode control circuit 44 through a resistance element R _A for preventing an overcurrent and a discharge. Further, a voltage V _F (=0 V) was applied to the focus electrode 15 from the focus-electrode control circuit 43 through a 1 kΩ resistance element R _F . The above resistance elements R _A and R _F are placed outside the display. Further, the electrostatic capacity “C” between the field emission device (more specifically, the focus electrode 15 ) and the anode electrode 35 is 70 pF. Further, the electric resistance value R _D along a discharge current path (specifically, the electric resistance value of the anode electrode 35 made of aluminum and the focus electrode) is 0.1 Ω. The anode electrode 35 had a size of 130 mm×100 mm.

Discharge currents “i” were calculated at an R _A =100 kΩ and R _A =1 kΩ, and FIGS. 28 and 29 show the results. The calculations disregarded inductance components. When FIGS. 28 and 29 are compared, it is seen that almost no discharge current “i” flows in the resistance elements R _A and R _F but that it flows in a closed system constituted of the anode electrode 35 , the discharge current path, the focus electrode 15 and the electrostatic capacity “C” as shown by an arrow and comes to be extinct.

The relationship of the total energy “Q” required for vaporization of the resistance layer 36 for controlling a discharge current, which resistance layer 36 has a thickness of t _R (unit: μm), and the energy (which will be called “discharge energy” and is (½)C·V _A ² hereinafter) generated on the basis of the electrostatic capacity “C” formed between the anode electrode and the field emission device, and the relationship of the resistance layer 36 having a thickness of t _R (unit: μm) and the discharge energy (½)C·V _A ² will be explained below.

FIG. 7 schematically shows a discharge state found when the resistance layer 36 for controlling a discharge current is formed in a discharge current path, and FIG. 8 shows an equivalent circuit found when a discharge takes place between the anode electrode 35 and the focus electrode 15 when the resistance layer 36 is provided as shown in FIG. 1.

For example, it can be considered that the display has no critical problem caused on its display function so long as a discharge that occurs between the anode electrode 35 and the focus electrode 15 does not cause the anode electrode 35 made of aluminum to vaporize to such an extent that an area corresponding approximately to one pixel is vaporized. It can be therefore also considered that so long as the discharge between the anode electrode 35 and the focus electrode 15 does not cause the resistance layer 36 to vaporize to such an extent that an area corresponding to one pixel vaporizes, the display has no critical problem caused on its display function.

That is, it can be said that so long as the discharge energy (½)C·V _A ² [in which “C” is an electrostatic capacity (unit: F) between the field emission device and the anode electrode and V _A is a voltage (unit: V) applied to the anode electrode 35 ] does not exceed the total energy “Q” required for vaporization of the resistance layer 36 having an area of π×r _R ² (unit: mm ² ) and a thickness of t _R (unit: μm), the resistance layer 36 is not damaged. That is, it is sufficient to satisfy the following expression (1).
Q >(½) C·V _A ² (1)

When a material constituting the resistance layer 36 vaporizes from a solid phase through a liquid phase, the total energy “Q” required for vaporization of the resistance layer 36 can be expressed by:

$Q\approx \pi ·t_R·r_R^2·d_R\times \left[C_{\mathrm{m\_S}}\left(T_L-T_r\right)+Q_{\mathrm{S\_L}}+C_{\mathrm{m\_L}}\left(T_G-T_L\right)+Q_{\mathrm{L\_G}}\right]\times {10}^{-6}$

Alternatively, when a material constituting the resistance layer 36 vaporizes from a solid phase directly, it can be expressed by:
Q≈π·t _R ·r _R ² ·d _R ×[C _{m — S} ( T _G −T _r )+ Q _{L — G} ]×10 ⁻⁶

In the above expressions,

• r _R : a radius (mm) of a vaporization-allowable region of the resistance layer, or a radius (mm) of a size (region) that does not cause a problem on the display function of a display even when the resistance layer of such a size (region) vaporizes, or a radius (mm) of that size (region) of the resistance layer which corresponds to 1 subpixel,
• d _R : a density (g·cm ⁻³ ) of a material constituting the resistance layer,
• C _{m — S} : a specific heat (J·g ⁻¹ ·K ⁻¹ ) of a material constituting the resistance layer in a solid state,
• T _L : a melting point (° C.) of a material constituting the resistance layer,
• T _r : room temperature (° C.),
• Q _{S — L} : a heat of solution (J·g ⁻¹ ) of a material constituting the resistance layer,
• C _{m — L} : a specific heat (J·g ⁻¹ ·K ⁻¹ ) of a material constituting the resistance layer in a liquid state,
• T _G : a boiling point (° C.) of a material constituting the resistance layer.

Further, when the material constituting the resistance layer vaporizes from a solid phase through a liquid phase,

• Q _{L — G} : a heat of vaporization (J·g ⁻¹ ) of a material constituting the resistance layer.

When a material constituting the resistance layer vaporizes from a solid phase directly,

• Q _{L — G} : a sum (J·g ⁻¹ ) of a heat of vaporization and a heat of solution of a material constituting the resistance layer.

When the resistance layer 36 is made of carbon, carbon vaporizes from a solid phase directly,

• d _R : 2.3 (g·cm ⁻³ )
• C _{m — S} : 6 (J·mol ⁻¹ ·K ⁻¹ )
• T _r : 30 (° C.)
• T _G : 3400 (° C.)
• Q _{L — G} : 350 (kJ·mol ⁻¹ ).

The total energy “Q” required for vaporization of the resistance layer 36 made of carbon is calculated as shown in the following expression (5), in which units of r _R and t _R are mm and μm, respectively.
Q =7.10×10 ⁻² ×π×r _R ² ×t _R ( J ) (5)

When C=70 pF and when V _A =10 kV, the following expression (6) can be obtained from the expressions (1) and (5).
π× r _R ² ×t _R >4.93×10 ⁻² (6)

Further, when π×r _R ² =0.04 mm ² (this area is approximately as large as an area of one subpixel), it is sufficient that the thickness t _R of the resistance layer 36 should satisfy the following expression (7).
t _R >1.2(μm) (7)

Further, when the anode electrode 35 is divided into 10 anode electrode units, C=7 pF, so that it is sufficient that the thickness t _R of the resistance layer 36 should satisfy t _R >0.12 (μm).

Further, π×r _R ² =0.04 mm ² is substituted in the expression (5), the following expression (8) can be obtained from the expression (1).
2.84×10 ⁻³ ×t _R >(½) C·V _A ² (8)

When the resistance layer 36 for controlling a discharge current is made of ITO, ITO having a relatively high volume resistivity has an SnO ₂ content close to 100%, so that it can be considered that ITO has physical property values almost equivalent to those of SnO ₂ . Therefore, the following physical property values of SnO ₂ are used as substitutes for the physical property values of ITO. ITO vaporizes from a solid phase through a liquid phase.

• d _R : 6.4 (g·cm ⁻³ )
• C _{m — S} : 53 (J·mol ⁻¹ ·K ⁻¹ )
• T _L : 1130 (° C.)
• T _r : 30 (° C.)
• Q _{S — L} : 48 (kJ·mol ⁻¹ )
• C _{m — L} : 53 (J·mol ⁻¹ ·K ⁻¹ )
• T _G : 1850 (° C.)
• Q _{L — G} : 314 (kJ·mol ⁻¹ )

Therefore, the total energy “Q” required for vaporization of the resistance layer 36 made of ITO is calculated as shown in the following expression (9), in which units of r _R and t _R are mm and μm, respectively.
Q =1.94×10 ⁻² ×π×r _R ² ×t _R ( J ) (9)

When C=70 pF and when V _A =10 kV, the following expression (10-1) can be obtained from the expressions (1) and (9). Further, when the anode electrode is divided into ten anode electrode units, and when C=7 pF and V _A =10 kV, the following expression (10-2) can be obtained from the expressions (1) and (9).
π× r _R ² ×t _R >1.8×10 ⁻¹ (10-1)
π× r _R ² ×t _R >1.8×10 ⁻² (10-2)

Further, when π×r _R ² =0.04 mm ² , it is sufficient that the thickness t _R of the resistance layer 36 should satisfy the following expressions (11-1) and (11-2) on the basis of the expressions (10-1) and (10-2).
t _R >4.5(μm) (11-1)
t _R >0.45(μm) (11-2)

Further, when π×r _R ² =0.04 mm ² is substituted in the expression (9), the following expression (12) can be obtained from the expression (1).
7.8×10 ⁻⁴ ×t _R >(½) C·V _A ² (12)

As a result, it is seen that if it is taken into account that the thickness of the resistance layer 36 for controlling a discharge current varies, it is sufficient that the thickness t _R (unit: μm) of the resistance layer 36 should satisfy the following expression (2) on the basis of the expressions (8) and (12).
t _R ×10 ⁻² >(½) C·V _A ² (2)

The expression (2) is not dependent upon the volume resistivity of a material constituting the resistance layer 36 for controlling a discharge current but is dependent upon physical property values such as d _R , C _{m — S} , T _L , Q _{S — L} , C _{m — L} , T _G , and Q _{L — G} .

When the thickness t _R of the resistance layer 36 for controlling a discharge current is defined as shown by the expression (2), the occurrence of damage on any region having an area of over 0.04 mm ² can be suppressed in the resistance layer 36 even when a discharge takes place between the anode electrode 35 and the focus electrode 15 . Further, damage on the anode electrode 35 can be also suppressed.

For example, it can be considered that the display has no critical problem caused on its display function so long as the discharge between the anode electrode 35 and the focus electrode 15 does not cause the anode electrode 35 made of aluminum to vaporize to such an extent that a portion having an area of π×r ₀ ² =0.04 mm ² (an area corresponding approximately to an area of 1 subpixel as described already) vaporizes.

The electric resistance value required of the resistance layer 36 for suppressing the vaporization of the above anode electrode 35 will be explained below. The explanation can be also applied to the focus electrode 15 .

A discharge current energy E(r ₀ ) generated by a discharge current “i” in the anode electrode 35 or the focus electrode 15 can be determined by the following expression.

That is, a discharge current energy ΔE to be generated in a micro region positioned at a distance of a radius r from a discharge point as an origin (radially width Δr) can be represented by the following expression (13-1), in which

• ρ ₀ : a volume resistivity (Ω·m) of an anode electrode or a focus electrode, and
• s ₀ : a thickness of the anode electrode or the focus electrode.

$\begin{array}{cc}\begin{array}{c}\Delta E=\int {\rho }_0·\Delta r/\left(2\pi ·r·s_0\right)·i^{2}dt\\ =\int i^{2}dt·\int \left[{\rho }_0·1/\left(2\pi ·r·s_0\right)\right]dr\end{array}& \left(13\text{-}1\right)\end{array}$

When the radius r is integrated from (D/2) to r ₀ , the following expression (13-2) can be obtained, in which

• r ₀ : a radius (μm) of a region in which the anode electrode or the focus electrode suffers damage due to a discharge, and
• D: a diameter (μm) of a plasma generated by the discharge.
  E ( r ₀ )=ρ ₀ ·(2 πs ₀ ) ⁻¹ ·ln(2 r ₀ /D )·∫ i ² dt (13-2)

As described already, it can be considered that the display has no critical problem caused on its display function so long as the discharge between the anode electrode 35 and the focus electrode 15 does not cause the anode electrode 35 made of aluminum to vaporize to such an extent that a portion having an area of π×r ₀ ² =0.04 mm ² (an area corresponding approximately to an area of 1 subpixel) vaporizes.

An energy found when a portion having an area of π×r ₀ ² =0.04 mm ² is vaporized by a discharge between the anode electrode 35 and the focus electrode 15 in the anode electrode 35 made of aluminum will be calculated below. The calculation will be based on values shown in the following Table 1. While the thickness of the anode electrode is assumed to be 1 μm (=s ₀ ), the anode electrode frequently has such a thickness in portions other than a portion on the phosphor layer.

	TABLE 1
	Thickness of anode electrode	1	μm (=s 0 )
	Melting area	0.04	mm 2 (=π × r 0 2 )
	Density of aluminum	2.7	g · cm −3
	Melting point of aluminum	660°	C.
	Boiling point of aluminum	2060°	C.
	Specific heat of aluminum	0.214	cal · g −1 · K −1
	Heat of solution of aluminum	94.6	cal · g −1
	Heat of vaporization of aluminum	293	kJ · mol −1
		=10850	J · g −1

A mass M _A1 (unit: gram) of aluminum melted, an energy Q _MELT (unit: Joule) required for aluminum reaching its melting point (660° C.) from room temperature (30° C.), an energy Q _Liq (unit: Joule) required for melting, an energy Q _Biol (unit: Joule) required for reaching a boiling point (2060° C.) from the melting point (660° C.), an energy Q _Evap required for vaporization and a total energy Q _Total required for vaporization are as follows. A specific heat of aluminum in a solid state is used as a specific heat of aluminum in Q _Biol for convenience.

$\begin{array}{c}{M}_{\mathrm{Al}}=0.04\times {10}^{-2}\times {10}^{-4}\times 2.7\\ =1.08\times {10}^{-7}\left(g\right)\end{array}$ $\begin{array}{c}{Q}_{\mathrm{MELT}}=0.214\times 4.2\times \left(660-30\right)\times M_{\mathrm{Al}}\\ =6.1\times {10}^{-5}\left(J\right)\end{array}$ $\begin{array}{c}{Q}_{\mathrm{Liq}}=94.6\times 4.2\times M_{\mathrm{Al}}\\ =4.3\times {10}^{-5}\left(J\right)\end{array}$ $\begin{array}{c}{Q}_{\mathrm{Biol}}=0.214\times 4.2\times \left(2060-660\right)\times M_{\mathrm{Al}}\\ =1.36\times {10}^{-4}\left(J\right)\end{array}$ $\begin{array}{c}{Q}_{\mathrm{Evap}}=10850\times M_{\mathrm{Al}}\\ =1.17\times {10}^{-3}\left(J\right)\end{array}$ $\begin{array}{c}{Q}_{\mathrm{Total}}=Q_{\mathrm{MELT}}+Q_{\mathrm{Liq}}+Q_{\mathrm{Biol}}+Q_{\mathrm{Evap}}\end{array}$